1. Field of the Invention
The present invention relates to an electrophotographic photosensitive member. More particularly, the present invention relates to an electrophotographic photosensitive member which contains an azo pigment having a specified structure in a photosensitive layer.
2. Related Background Art
Known organic photoconductive substances for electrophotographic photosensitive members include photoconductive polymers represented by poly-N-vinylcarbazoles, and low molecular-weight organic photoconductive substances like 2,5-bis(p-diethylaminophenyl)-1,3,4-oxadiazole, and further, combinations of such an organic photoconductive substance, and a dye or a pigment.
Electrophotographic photosensitive members employing an organic photoconductive substance have the advantages of being provided advantageously at high productivity and at low product price owing to relatively low material cost and a coating production method, and the sensitivity thereof can be arbitrarily controlled. Accordingly, electrophotographic photosensitive members have been investigated comprehensively. Recent development of a function-separation type of photosensitive member, which is constituted of lamination by a charge-generating layer containing an organic photoconductive dye or pigment, and a charge-transporting layer-containing an aforementioned photoconductive polymer or a low-molecular organic photoconductive substance, has achieved remarkable improvement in sensitivity and durability of conventional organic electrophotographic photosensitive members.
Azo pigments have excellent photoconductivity. Various characteristics thereof can readily be obtained by combination of an azo component with a coupler component. Accordingly a number of azo pigments have heretofore been reported. The examples are described in Japanese Patent Laid-open Application Nos. 57-116345, 58-95742, etc. The electrophotographic photosensitive members employing such an azo pigment, however, are not satisfactory in sensitivity and potential stability in repeated use.